1. Field Of The Invention
The present invention relates to a domestic refrigerator with "plaques" formed in the refrigerator cabinet walls to prevent thermal bowing of the cabinet.
2. Description Of The Prior Art
A current state of the art domestic refrigerator cabinet consists of an exterior prepainted steel shell, an interior plastic liner for dividing the cabinet interior into a fresh food compartment and a frozen food compartment, and a layer of foam between the metal shell and the plastic liner which acts as thermal insulation and provides structural rigidity to the refrigerator cabinet.
The inner liner may be formed to provide any of the common refrigerator configurations, including the top-mount type in which a horizontal separator divides the unit into an upper frozen food compartment and a lower fresh food compartment, the bottom-mount type which is essentially the inverse of the top-mount type, and the side-by-side type in which a central vertical separator divides the unit into side by side fresh and frozen food compartments.
Thermal bowing of the cabinet sidewalls is a serious problem in the above described refrigerator cabinets. It is believed that the temperature gradient which exists across the cabinet wall produces a bi-material effect, where the various materials in the cabinet wall expand or contract by a different amount in response to the temperature gradient. The interior plastic liner is exposed to the cooled interior of the refrigerator compartments, and the liner surface therefore tends to contract slightly. The exterior shell is exposed to a warm ambient temperature, and therefore tends to expand. Although the liner and shell surfaces respond differently to the thermal effects, they are locked together by the foam layer and may not move freely with respect to one another. As a result, the cabinet sidewalls tend to bow outward to compensate for the expansion and contraction of the different layers of the walls.
The bowing is generally more severe in cabinet walls adjacent to the frozen food compartment than in those adjacent to the fresh food compartment due to the greater temperature gradient across the freezer compartment walls. Side-by-side refrigerators are more susceptible to cabinet bowing than top-mount or bottom-mount cabinets because the side-by-side cabinet is divided vertically by a compartment separator wall, and lacks the horizontal divider of the top- or bottom-mount which to some extent ties the cabinet sidewalls together. Bowing of the cabinet sidewalls is of particular concern because the compartment shelves are sometimes mounted between the opposed sidewalls of the compartment, and when the cabinet bow is excessive the shelves are unable to span the increased distance and may collapse. Other detrimental effects of cabinet bowing include misalignment of the cabinet doors and door seals, misactivation of door-actuated switches, and increased energy consumption due to air leakage around the doors.
It is generally known in the art that refrigerator liners may have various forms of embossing and indentations for purposes such as to cover manufacturing imperfections in refrigerator liner sidewalls, to provide incremental increases in refrigerator volume, or to provide enhanced visual aesthetics in the refrigerator liner. However, it was not known previously that the presently disclosed plaques may be used to prevent cabinet bowing. U.S. Pat. No. 2,028,943 (Money) discloses a stamped metal refrigerator liner with raised ridges to increase the rigidity of the sidewalls, however this patent is not directed to reducing deformation of the entire cabinet wall. U.S. Pat. No. 4,053,972 (Kordes) shows a refrigerator door with apparently decorative rectangular liner indentations. U.S. Pat. No. 4,498,713 (Fellwock et al) discloses horizontal and vertical stress-relief ribs in a refrigerator cabinet liner. U.S. Pat. No. 4,914,341 (Weaver et al) discloses that horizontal ribs in a refrigerator door liner are effective to reduce door liner stress.